This invention relates to marine propulsion systems of the kind which includes a power-driven screw propeller having blades of adjustable pitch, the propeller being mounted on a propeller shaft driven by an engine or other prime mover in a vessel.
An object of the present invention is to provide an improved marine propulsion system of the aforesaid kind which is simple and economical to manufacture, and which enables conventional components, and existing standard parts, components and assemblies to be utilised in a novel manner in its manufacture.
Another object of the invention is to provide a marine propulsion system of the aforesaid kind having a two-position setting of the blade pitch angle and a simple mechanical system for selectively effecting the pitch setting.
In known systems of the kind referred to, hydraulic or mechanical pitch control means is provided which can be operated to adjust the blade pitch angle into any setting in an infinitely-variable range extending from full-ahead pitch to full-astern pitch. The propeller shaft drive is usually transmitted from the prime mover to the shaft through a speed-reduction gearbox, which may not provide a reverse drive, and to effect reverse propulsion the blades are adjusted into a reverse-pitch angle setting.
Another object of the invention is to provide a marine propulsion system of the aforesaid kind having a two-position setting of the blade pitch angle, which settings respectively correspond to coarse-pitch and fine-pitch blade angles, in conjunction with a reversible reduction gearbox which enables either forward or reverse propulsion of the associated vessel to be effected with the blades in either setting.
A yet further object of the invention is to provide a simple pressure-fluid-operated actuator which can be incorporated between the reduction gearing and the propeller shaft in a marine propulsion unit of the kind aforesaid and by which the selective adjustment of the blade pitch into either of two predetermined settings can be effected.